From 0602b3e4e73ad7124d1c1a389bf38b99c8717cff Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 8 Jan 2016 09:35:51 -0800 Subject: [PATCH] ipv6: tcp: add rcu locking in tcp_v6_send_synack() commit 3e4006f0b86a5ae5eb0e8215f9a9e1db24506977 upstream. When first SYNACK is sent, we already hold rcu_read_lock(), but this is not true if a SYNACK is retransmitted, as a timer (soft) interrupt does not hold rcu_read_lock() Fixes: 45f6fad84cc30 ("ipv6: add complete rcu protection around np->opt") Reported-by: Dave Jones Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- net/ipv6/tcp_ipv6.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 01706792f282..b20f7a08b4f7 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -513,8 +513,10 @@ static int tcp_v6_send_synack(struct sock *sk, struct request_sock *req, __tcp_v6_send_check(skb, &treq->loc_addr, &treq->rmt_addr); ipv6_addr_copy(&fl6.daddr, &treq->rmt_addr); + rcu_read_lock(); err = ip6_xmit(sk, skb, &fl6, rcu_dereference(np->opt), np->tclass); + rcu_read_unlock(); err = net_xmit_eval(err); } -- 2.39.2